US3495577A - Self-contained hydraulic tappet - Google Patents

Description

Feb. 17, 1970 c. lHl coLLlNs SELF-CONTAINED HYDRAULIC TAPPET.

FiledFeb. 7, 1968 nd/M- United States Patent O 3,495,577 SELF-CONTAINED HYDRAULIC TAPPET Clifford H. Collins, Monterey Park, Calif. (718 Meats Ave., Orange, Calif. 92667) 'Filed Feb. 7, 1968, Ser.No. 703,693

' Int. Cl. F011 1/00, 1/20 U.S. Cl. 123-90 3 Claims ABSTRACT 0F THE DISCLOSURE BACKGROUND OF THE INVENTION The present invention relates generally to hydraulic valve lifters or tappets found in valve operating mechanism for internal combustion engines and the like and more especially to a tappet which is self-contained, that is, it has no connection to an external source of hydraulic uid under pressure.

As is well known in the field of internal combustion engines, hydraulic tappets are a preferred means of compensating for changes in the length of valve stems due to thermal expansion and contraction. The hydraulic valve lifter is a means for operating the valve without any lash or clearance between the parts; and, consequently,

has come into widespread use in all types of internal combustion engines. v

' Known types of hydraulic valve lifters are connected to the oil feed system of the engine and receive oil under pressure from the engine pump. This same oil is circulated throughout the bearings to supply lubricant to the moving parts. This oil under pressure serves as hydraulic uid in the tappets and the connection to a pressure source insures that the tappet is full under normal running conditions.

This system of hydraulic tappets is expensive to incorporate in an internal combustion engine since the system requires complicated coring and/or drilling of small oil supply passages. Since oil is supplied to each tappet and there are two tappets for each cylinder, numerous passages are required in a multiple cylinder engine. The effort and expense involved in providing the passages is substantially greater, in most engines, than the cost of the tappets themselves so that a major part of the total expense is that required in preparing the engine block.

There are also collateral problems such as keeping the oil passages clean and free from plugging with debris or sludge. Also, the problem of keeping the oil supply to the tappets clean so that these tappets do not stick as a result of accumulation of sludge and gum inthe tappets derived from the oil supplied to them.

Thus, it is a general object of the present invention to provide a hydraulic valve lifter or tappet which has the ability to operate in the desired manner but without any connection to the engine oil system.

More particularly, it is an object of the present invention to reduce the cost of the valve operating mechanism in an engine or the like by eliminating the need for passages in the engine block supplying oil under pressure to the tappet by making the tappet a self-contained unit.

It is also an object of the present invention to provide Y 3,495,577 Paierited Feb. 17, 1970 ICC a self-contained hydraulic tappet having its own internal oil supply which is completely sealed within the tappet body and remains clean throughout the life of the tappet.

SUMMARY OF THE INVENTION These and other objects of the invention not particularly mentioned herein are obtained in an hydraulic tappet constructed according to the present invention which comprises a sealed housing, a piston movable within the housing, a body of hydraulic fluid within the housing, and means, including a movable valve member, providing controlled circulation of uid within the housing between opposite sides of the piston. The tappet also includes resilient means biasing the piston in one direction whereas the valve means includes a movable member which is moved to close a uid passage to ow of the hydraulic lluid when relative motion of the piston is in the direction opposite to the biasing force applied to the piston by the resilient means.

In a preferred embodiment, the movable valve member of the valve means is a plate which is biased to an open position and which is closed by movement of the hydraulic fluid relative to the piston in such a manner as to close a uid passage through the Ipiston during the desired portion of the operating cycle so that the tappet is able to transmit force from the cam shaft to the valve stem or similar member. This plate valve is porous to permit limited uid flow through the plate from the high pressure side thereof, thereby allowing the tappet to shorten slightly during each cycle and correcting for overexpansion of the tappet due to the resilient means. The change in tappet length is accompanied by changes in volume of the space between the tappet and the end wall of the housing with consequent circulation of uid from one side of the piston to the other.

DESCRIPTION yOF THE DRAWING FIG. 1 is a longitudinal median section through a hydraulic valve lifter constructed according to the present invention; and

FIGS. 2 and 3 are each median semi-sections showing alternate positions of the internal parts of the hydraulic tappet.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawing, it will be seen in FIG. 1 that the hydraulic valve lifter comprises a housing indicated generally at 10. This housing 10 includes cylinder 11 which is closed at one end by end wall 12. At the other end of the cylinder is the cover 14 which is provided with an integral hollow stern 14a. Stem 14a is preferably provided with external threads 15 by means of which the tappet may be mounted on a rocker arm, as is indicated diagrammatically at 16. Alternatively, the external surface of stem 14a can be smooth and is held within a bearing or guide which strains the hydraulic tappet to axial movement.

Inside housing 10 is piston 18 which has a snug sliding t with the interior surface of the wall of cylinder 11. vIf desired, some sealing means, such as an O-ring 19, may be provided on the cylinder to provide a iluidtight seal between the piston and the cylinder wall.

Piston 18 is biased in one direction within the housing by a helical coil spring 20 which bears at one end against a face on the piston and at the other end against end wall 12. Spring 20 normally keeps piston 18 at or near one end of cylinder 11, in this case the upper end. It will Ibe understood that in referring to any direction, such as up and down, such reference is solely for descriptive purposes and in connection with the hydraulic tappet in the aspect illustrated in the drawing. In use, the tappet can be inverted from the position shown in which case the descriptive terms referring to directions would be obviously reversed.

In order to obtain good bearing with the cylindrical wall on the housing, the piston 18 has a relatively long skirt, thus providing a comparatively deep annular groove 18a in the piston body in which spring 20 is located. This arrangement is preferred since it permits a relatively longer spring to be used without increasing the overall length of the valve lifter.

Cavities within the housing are filled by a body of oil or other hydraulic uid, referred to generally at 22. This hydraulic Huid may be of any suitable viscosity or chemical composition. As will be further explained, the hydraulic fluid circulates within the housing between opposite sides of the piston 18 and means are provided within the housing for controlling circulation of the hydraulic fluid as it passes from one side of the piston to the other.

One element of such circulation control means is a movable valve member 24 in the form of a circular plate, located at one end of piston 18. The -piston has an axially extending fluid passage 23 extending through the piston from one side to the other; and valve plate 24 is adapted to engage a. surface on the piston at one end of the uid passage in order to close the fluid passage when the valve plate is in the position illustrated in FIG. l.

The movable valve member is held loosely in place with respect to uid passage 23 by cage 25 mounted on the body of piston 18. This cage is a cylindrical member which is provided with a plurality of spaced, inwardly turned lugs 25a which engage valve plate 24 in order to limit its travel away from the piston to open passage 23, as shown in FIG. 3. Cage 25 is cut-away between the lugs 25a; and these cutouts (FIG. 3), in combination with clearance between the periphery of plate 24 and the internal surface of cage 25 permits free downward travel of iluid out of piston passage 23, around the periphery of the plate, and thence either through the cutouts or between the lugs 25a when the valve plate is in the open position of FIG. 3 away from the piston body.

Valve plate 24 is a porous member, such as may be obtained by a sintered product which allows limited pas sage of hydraulic fluid through the plate, under pressure. Thus, when the plate is against the piston body and closes the end of piston iluid passage 23, as illustrated in FIG. l, there is still a limited ow of iluid through the plate and upwardly into passage 23 from the space within the housing below the piston when uid under the piston is under pressure.

At the end of piston 18 opposite spring 20, the piston is provided with a circular recess 28; and in the base of the recess is a plurality of undercuts as indicated at 28a. Recess 28 receives seat member 29 which is adapted at one face to bear against the piston at the bottom of recess 28. There is limited clearance around the periphery of the major -diameter of seat 29 and the wall of the recess 28 -so that this clearance together with undercuts 28a provide a fluid passage which is always open to permit free flow of hydraulic fluid between piston passage 23 and the space within the housing above piston 18, that is at the end of the housing toward which spring urges the piston. The upper end of seat member 29 is provided with a seat which is preferably of spherical conguration which receives the rounded lower end of push rod 30. By virtue of the force of spring 20, seat member 29 is always urged against push rod 30. As shown in FIG. l, push rod 30 at the other end bears against valve stem 31.

A exible diaphragm or seal 32 is located at the upper end of the cylinder cavity and engages the walls of cylinder 11 with a Huid-tight tit. The seal has a central opening through which seat member 29 passes, a tight lit between the seal and the seat member being obtained by providing an annular peripheral groove in the seat member to receive the wall of the seal, as shown clearly in FIG. l. Seal 32 is not only ilexible but preferably elastic so that it may stretch when the piston moves to the ex- 4 treme downward position within cylinder 11 that is illustrated in FIG. 2.

Having described the construction of a preferred embodiment of the invention, its operation will now be set forth. As the hydraulic tappet is moved by rocker arm 16 toward valve stem 31, which is the direction of movement which normally causes the valve on stem 31 to be opened, the parts of the hydraulic tappet occupy positions substantially as illustrated in FIG. l. The movement of the housing is upward relative to piston 18 and this movement tends to reduce the volume within the housing below the piston. The flow of hydraulic uid from below the piston through central passage 23 closes valve 24, thereby producing the solid effect and transmitting through the piston to push rod 30 a thrust against valve stem 31.

The forces in the hydraulic tappet which tend to reduce the volume at the lower end of the piston subject the hydraulic uid to a relatively high pressure and a small amount of the lluid passes through the porous valve plate by way of passage 23 into the housing space above the piston. This transfer of iluid is accomplished without any clearance forming between the parts and during the transmission of thrust to push rod 30. In this manner, hydraulic uid is transferred to the upper end of the housing. If the duration of the stroke against valve stem 30 is long enough, piston 18 will be moved to the bottom of the housing to the position shown in FIG. 2.

During the return stroke of rocker arm 16, the movement of the hydraulic tappet is away from the valve stem 31, the valve stem of course maintaining contact with push rod 30 by virtue of the conventional spring which closes the valve to which stem 31 is attached. As the hydraulic tappet is' moved downwardly in the drawing under the influence of rocker arm 16, spring 20 is able to move piston 18 upwardly within the housing. This causes relative displacement of the luid from above the piston to below the piston and the motion of hydraulic fluid through iluid passage 23 opens valve 24, carrying valve plate downwardlyk to rest against lugs 25a and shown in FIG. 3. Once the valve member 24 is moved away from the end of the piston and uid can flow through passage 23, upward movement of the piston within the housing is relatively rapid because of the low resistance to iluid movement and the piston then returns upwardly from the position of FIG. 2 with the valve open as shown in FIG. 3.

During the next operation of the valve, the cycle of movement within the hydraulic tappet is repeated.

From the foregoing description, it will be apparent that various changes in the detailed construction, design, and arrangement of the elements of the improved hydraulic valve lifter may occur to persons skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the foregoing description is considered as being illustrative of, rather than limitative upon, the invention disclosed herein.

I claim:

1. A self-contained hydraulic tappet for Valve operating mechanisms, comprising:

a sealed housing;

a piston movable within the housing;

a body of hydraulic fluid within the housing; and

means including valve means providing controlled circulation of iluid within the housing from one side of the piston to the other and return;

the circulation means including:

a fluid passage extending longitudinally through the piston;

and a valve plate at one end of the passage movable to close the fluid passage to restrict fluid flow in one direction, said plate being porous to permit limited fluid flow through the plate.

2. A self-contained hydraulic tappet as claimed in claim 1 which also includes:

spring means bearing at one end against the housing and at the other end against the piston to bias the piston in one direction;

a seat member bearing against a surface on the piston at the side thereof remote from the spring means and partially closing the ud passage to Huid ow, said seat member having an outwardly facing concave surface engageable with a push rod;

a exible seal engaging the seat member to expose the concave surface thereon and also engaging the housing around the periphery of the seal; and

a push rod guide mounted on said housing exteriorly of said exible seal to hold the seal in place.

3. A self-contained hydraulic tappet as claimed in claim 1 that also includes:

a cage carried by the piston and surrounding the valve plate to limit the travel of the plate Valve away from a closed position.

References Cited UNITED STATES PATENTS AL LAWRENCE SMITH, Primary Examiner

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